The present invention relates to an electric field therapeutic apparatus, and more particularly, to an apparatus which can provide a high potential (100-5,000V) electric field to an injured site of a human or animal body via electrodes isolated electrically from the environment, so as to promote healing of injured tissues such as fractured bone and wounded soft tissues.
The piezoelectric effects of bone, muscle and other soft tissues of human and animal body have long been researched by the medical and piezoelectric researchers. Generally speaking, the biopolymers, like all the other piezoelectric materials, exhibit the piezoelectric effects, namely, they will be electrically is understood that the researching and utilizing of the biopolymer's piezoelectric effect are of significant importance for understanding the mechanism of a living body's growth and for promoting the biomedical progress. The inventors of the present invention have made an extensive effort in this field, one of the inventors Mr. Zhang Fuxue, is the coauthor of the book "PIEZOELECTRICITY", published by Defence Industry Publishing House, Beijing, 1984. The disclosure of Chapter 30, Volume II, PP 623-673 of this book is incorporated herewith by reference.
It is known from the above-mentioned book that the experiments have been made to show that a human or animal bone is charged with negative electricity on its surface when it is oppressed by external stress, it is further proved that a bone with negative charge will exhibit an active growth, and similar thing can happen to other soft tissues. It is believed that a change of the electrical environment at a bone fracture will promote the healing of the fractured bone and other injured tissues, and the piezoelectric effect of the bone and other tissues contribute to this healing. The phenomena of a bone's piezoelectric effect are used to explain why physical exercises promote the metabolism of bone tissue and accelerate the healing of injured tissues. On the other hand, since the piezoelectric effect is reversible, it suggests that if an external electric field is formed adjacent a bone fracture, it can also accelerate the healing of injured tissues.
According to what is mentioned above, a foil electret is used to form an external electric field adjacent a bone fracture, so as to promote the healing of the fractured bone. Reference can be made to "Promote Healing of Bone by Using Electret", by Wang Shoutai, STATIC ELECTRICITY TECHNIQUE, volume 1, 1984 PP 1-5. The problems of this method are that the electrical charge of a foil electret will be lost after some time, so that electret must be replaced regularly during the therapeutic period, and on the other hand, the range of the electric field strength produced by electret is too narrow and uncontrollable, so that strength of the electric field can not be adjusted to meet the patients' different conditions in clinical practice. All these problems made it difficult to use the electret widely in clinical practice.
In prior art, there is a kind of apparatus for healing fractured bone with interacting electric current and a magnetic flux field. This apparatus generates electric current pulses and magnetic field pulses to produce a net current in the region of the fractured bone and generally perpendicular to the plane of the fracture, as disclosed in U.S. Pat. No. 4,556,051, by Maurer.
It is known in the art that during the therapeutic period of injured tissues, especially fractured bone, there exists a contradiction between the fixing and moving of the injured body part. On one hand, the fractured bone should be well fixed to keep the fracture aligned and heal, that means to avoid any movement of the injured body part such as an injured limb, this is usually done by using plaster. On the other hand, during the relatively long time of this period, the blood circulation at the fixed part will be reduced and a local under-nutrition happens, the piezoelectric effect of the injured tissue will decrease because of lacking mechanical stress caused by body movement, all these will jeopardize the electrical environment of the bone fracture and result in myatrophy and arthocleisis of the injured body part, therefore, make the patient suffering more and longer.